returns the error_message in assertWorkflowTransitionFails

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@13849 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/tests/ERP5TypeTestCase.py

@@ -509,6 +509,7 @@ class ERP5TypeTestCase(PortalTestCase):
       if error_message is not None:
         self.assertEqual(str(workflow_history[-1]['error_message']), error_message)
       self.assertEqual(object.getSimulationState(), reference_workflow_state)
+      return error_message
 
 def setupERP5Site( business_template_list=(),
                    app=None,